Re: My Bus suddenly won't turn over...Any Ideas???
Where is the starter solenoid/relay mounted on this particular bus? Is it mounted right on the starter itself or is it remotely mounted? In either case there is a little diagnosis needed so the problem can be narrowed down. Now I would vote that this is a control side issue (ignition switch, solenoid, some sort of interrupt, etc), but we need to know for sure.
I'm hoping you have a multimeter. Use the multimeter and make sure you have 12 volts on the large battery cable coming from the battery to feed the solenoid. This will eliminate the power feed as a problem. Then, have someone turn the key and check to see that the "S" terminal on the solenoid (this will be the smaller control wire). Chances are you won't, but if you do then the solenoid becomes suspect (or possibly a whole starter). You probably will not which means it is time to trace wires. I wish it were as simple as just getting a wiring diagram, but it isn't. Verify that you have 12 volts feeding into the ignition switch. If you do not you might have an interrupt device in the circuit or a broken wire, etc before that. If you do not have power then I would run a 12 volt jumper wire to that power feed and see if the bus starts.
If you do have power to the switch then it is is time to dig deeper. Clearly there is something in the middle between the switch and the starter. Let me know when you figure it out.
One other thing. Don't take this the wrong way...I'm a mechanical person and got absolutely burnt by this before. Is the transmission in neutral or did someone maybe bump it into gear? This would explain the no crank (neutral safety switch) as well as the engine warn light.